When such an extracorporeal blood circuit is used, air bubbles may form inside the blood circuit. In addition, air which was included in the blood circuit on the putting into operation of the extracorporeal blood circuit can enter into the blood. An air bubble which enters into the patient's blood circulation can cause a fatal air embolism in the worst case.
This problem has been known for some time and there are different strategies to avoid air bubbles being located in the blood exiting the extracorporeal blood circuit via the arterial connection. There are, for example, air bubble detectors which can detect air bubbles in the blood stream. With the previously known systems, a visual or acoustic alarm signal is output on detection of an air bubble and the blood supply to the patient is stopped. Subsequently, the medical personnel on hand must act as fast as possible since the problem has to be eliminated and the patent has to be treated further. Equally, different components are known which should filter air bubbles out of the blood, for example blood filters which collect and retain both particles and gas bubbles.